1. Field of the Invention
The invention relates to devices for preparing and terminating optical fibers for interconnection in telecommunications networks using plug and socket assemblies that align the optical fibers for optimal signal transmission without the use of ferrules. More particularly, the present invention facilitates field processing of one or more cleaved and polished bare fiber ends using an apparatus for temporary containment during suitable preparation of terminal portions of optical fiber cables for field installation into the plug portion of an optical fiber plug and receptacle connector.
2. Description of the Related Art
The use of optical fibers in telecommunications networks offers the advantage of broader bandwidth when compared to the copper wire systems that have dominated this industry. Today's high speed, bandwidth-intensive computing environments provide justification for increased use of optical fiber cables. The demand for optical fiber is expected to increase as transmission protocols reach higher and higher speeds and bandwidth requirements continue to grow. Until recently, cost was a deterrent to the use of optical fiber systems. The impact of cost has become less severe because of improvement in the supporting electronics and optical communications infrastructure. In addition, an increase in the volume of optical fiber production has driven down the cost of optical fiber components and devices. Optical fiber systems will become the preferred choice as component and installation costs approach parity with copper wire systems.
As with copper wire, it is necessary to provide means for interconnection and termination of optical fibers. Interconnection of optical fibers may be achieved by a number of methods including the methods of splicing and connecting. A splice is generally understood to be the formation of a permanent connection between a pair of optical fibers. The act of connecting optical fibers requires a device, i.e. a connector that facilitates repeated engagement and disengagement of optical fibers. An optical fiber connector, for one or more optical fibers, typically includes a plug portion and a receptacle or socket portion. Insertion of the plug portion into the receptacle portion provides interconnection for optical signal transmission between optical fibers,. During the mating of a plug portion with a receptacle portion of an optical fiber connector, there is the need to provide accurate axial alignment of lengths of optical fiber for the number of optical fibers contained within each plug or receptacle. One requirement of an optical fiber connector is the joining together of lengths of optical fibers so aligned that light energy will propagate from one fiber to the other without insertion loss that may be observed as an appreciable light attenuation. To reduce insertion loss at the point of optical fiber connection, it is necessary to have precise registration and abutting fiber contact across the entire end of each optical fiber end face.
A broad range of devices exist for connecting and aligning optical fibers, whether the connection includes only a pair of optical fibers, i.e. one optical fiber in both the plug and receptacle portion of the optical fiber connector, or two or more fiber pairs. The majority of connectors include ferrules that rely on alignment of the outer surface of each ferrule to provide fiber alignment during termination, polishing and a positioning of each optical fiber end in an optical fiber connector.
A relatively recent development in optical fiber interconnection devices eliminates the need for ferrule-terminated optical fibers. These alternate plug and socket connectors use fiber guiding V-grooves to align cleaved and polished end portions of stripped optical fibers for optimum signal transmission. Connector assemblies using V-grooves for optical fiber alignment are adaptable to the needs of simplex (one fiber), duplex (two fibers), and multiplex (two or more fibers) connectors. They also offer advantages over ferrule-terminated optical fibers such as fewer component parts, smaller size and convenient assembly.
Further discussion emphasizes connector assemblies using V-groove alignment of optical fibers that undergo repeated engagement and disengagement. U.S. Pat. No. 5,381,498 describes a modular, multi-fiber connector comprising a plug and receptacle having an appearance similar to a conventional RJ 45 jack for copper conductors. The plug includes a body having a surface with several grooves that position and limit movement of otherwise free end portions of optical fibers. Fibers inside the receptacle are free to move into the grooves inside the plug body and into forcible abutment with the terminal ends of the plug fibers during insertion of the plug through an opening in the body of the receptacle. U.S. Pat. Nos. 5,757,997 and 6,026,210 and related patents, for example, describe subsequent development of connectors using V-groove alignment of optical fibers. These later versions of optical fiber connectors include features such as internal fiber splices using crimp elements, similar to those described in U.S. Pat. No. 5,638,477, and optical fiber holders of the type described in U.S. Pat. No. 6,078,719. Optical fiber holders become permanently applied around one or more optical fibers during fiber preparation using a device that cleaves stripped terminal portions of one or more optical fibers to a length determined by the dimensions of the optical fiber receptacle. The cleaving process has the capability for precise cleaving and polishing to produce multiple optical fibers having substantially the same length. U.S. Pat. Nos. 5,813,902, and 6,099,392 further describe systems and processes for cleaving and polishing terminal portions of optical fibers prior to assembly of connector receptacles or sockets in the field.
Implementation of optical fiber cable networks using cable interconnection based upon V-groove connectors requires field termination for either a connector receptacle or a connector plug or both. Field installation of optical fiber cables employs known methods for applying a receptacle or socket to a stripped end portion of one or more optical fibers. The lack of a corresponding method for field installation of connector plugs limits field-termination capability to optical fiber cables having a connector receptacle at each end. This limitation restricts optical fiber cable interconnection to a single option in which field-terminated cables, having connector receptacles at both ends, alternate with factory terminated cables, having connector plugs on both ends. Factory production of connector plug terminated optical fiber cables typically provides a limited variety of standard cable lengths. The use of pre-terminated standard lengths of optical fiber cable prevents the use of normal methods for installing optical fiber cable by pulling it through cable ducts or the like before applying connector plugs and sockets for interconnecting lengths of cable. Pre-terminated, factory assembled, optical fiber cables add expense and require more cable duct space than conventional cable systems. Reliance on standard lengths of terminated cables also denies the advantage of efficient use of space associated with custom installations. To provide more options and to facilitate installation of custom cable networks, there is a need for field installable optical fiber connector plugs so that cable network installers may choose whether to terminate a particular cable with either a connector plug or a connector socket.